Repairing my concrete water tank

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8 months 1 day ago #558981 by mattib
Hi all, have had a search through but cant quite find the answer, so hoping one of you might know the answer.

We have 2 water tanks, the original (probably 30+ year old) concrete and a plastic one the previous owner added a few years ago. The concrete water tank has developed a small hole about 2/3 the way up on one side, and is also weeping at a few points along the same side. We only bought the place about 6 months ago and have no idea when they were last cleaned so i am in the process of slowly draining the concrete tank to clean and repair. I would like to give it a go myself if possible as most quotes so far are ranging from $3-6k, most sites i have read up on recommend skim coating the inside wall of the tank with fresh mortar but i cant seem to find a potable water approved mortar readily available.

Has anyone here actually repaired their own tank from inside? If so what product did you use?

Living with my head in the clouds in the Waitakere Ranges

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8 months 21 hours ago #558983 by tonybaker
I guess you have googled it? Does it have a decent sized manhole for access to the inside? Is it filled from bore water or roof water?

5 acres, Ferguson 35X and implements, Hanmay pto shredder, BMW Z3, Countax ride on mower, chooks, Dorper and Wiltshire sheep. Bosky wood burning central heating stove and radiators. Retro caravan. Growing our own food and preserving it. Small vineyard, crap wine. :)

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8 months 19 hours ago #558985 by mattib
Yeah been doing plenty of googling and reading, most of the good info has overseas brands so a bit different to here.

Manhole is ok, pretty sure i will be able to contort my podgy gut into the cavity below though i havent tried it yet. I am just trying to get a plan in mind on how to attack it, suck out remaining water and gunk in bottom, waterblast and spray down with something, then mortar or some suggest a latex paint but i am not that keen on that if i can somehow keep it cement.

Living with my head in the clouds in the Waitakere Ranges

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8 months 16 hours ago #558986 by LongRidge
I have waterproofed a concrete tank with a two part filler that I obtained from a concrete tank maker. It was quite easy to use.
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8 months 15 hours ago - 8 months 15 hours ago #558987 by Hertz Donut
I've used Humebond (two-part epoxy) to repair concrete troughs with good results but no guarantees it'd be suitable for a water tank. Very simple to use.

Don't ask me, it was on its side when I got here.
Last edit: 8 months 15 hours ago by Hertz Donut.
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8 months 12 hours ago #558988 by tonybaker
Be careful when you are in there, and have someone outside to help if you get overcome by fumes.
What I did was drain the tank and get inside with a broom and hosepipe to clean the walls and floor. My tank has a drain outlet almost on the bottom so I swept the muck through there. You may have to search around the bottom for yours. Water blasting is good but you don't want anything electrical in there, use a plug in RCD adaptor on the plug. I wouldn't start with the waterblaster as you will end up with too much muck. Fix up all you inlet and outlet connections and fit an overflow if there isn't one already.
You can use Cemix waterproofer or this one to fix the cracks from the inside or use a bituminous product like this . I went with the last one and did my gutters as well. I used this product a lot in the old days to waterproof old galvanised roof tanks.
Before you refill the tank, consider making a floating outlet so that you are only taking the topmost water, I used a piece  of corrugated pipe like you have on a washing machine, with one end forced over the outlet pipe and the other end attached to a soft drink bottle. Drill a hole in the top of the tank for a float so you can see how much water is in there. Mine is another soft drink bottle attached to a fibreglass rod with a piece of polystyrene stuck on it as an indicator. Sounds like fun, eh!

5 acres, Ferguson 35X and implements, Hanmay pto shredder, BMW Z3, Countax ride on mower, chooks, Dorper and Wiltshire sheep. Bosky wood burning central heating stove and radiators. Retro caravan. Growing our own food and preserving it. Small vineyard, crap wine. :)
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8 months 11 hours ago #558989 by mattib
Thanks. I tried to use those water plug products externally to plug the hole as that was what was recommended, it did help but the water pressure was too much.

I was worried if i used the bitumen or latex roll on products there might be a risk of it not sticking to the concrete properly, flaking off and getting into the water. Is that not an issue? I am probably overthinking it.

Nice number 8 wire there with the floating intake! Its an old tank and i think the outlet is buried so was going to empty and asses what the outlet looked like as to whether a floating inlet could be added. I dont remember seeing any drainage outlet, i have a submersible pump and was going to use that to suck the majority of the remaining water out and then maybe wetvac the rest? Cant say im that keen to go drilling too much into the old concrete if i dont have to, but i had been toying with the idea of fitting overflow vacuum pipes inside to try and keep up the water quality.

Living with my head in the clouds in the Waitakere Ranges

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8 months 6 hours ago #558992 by tonybaker
Thanks. I tried to use those water plug products externally to plug the hole as that was what was recommended, it did help but the water pressure was too much. They only work on the inside

I was worried if i used the bitumen or latex roll on products there might be a risk of it not sticking to the concrete properly, flaking off and getting into the water. Is that not an issue? I am probably overthinking it. I have used it and it sticks to damp surfaces ok.
Nice number 8 wire there with the floating intake! Its an old tank and i think the outlet is buried so was going to empty and asses what the outlet looked like as to whether a floating inlet could be added. Once you are inside you will see it around the bottom somewhere, there is usually a groove in the floor so that it fully drains the tank. I dont remember seeing any drainage outlet, i have a submersible pump and was going to use that to suck the majority of the remaining water out and then maybe wetvac the rest? Sounds like a good plan Cant say im that keen to go drilling too much into the old concrete if i dont have to, You only need a small hole to suit the rod, mine is 8mm only but i had been toying with the idea of fitting overflow vacuum pipes inside to try and keep up the water quality. You will get good clean water with a floating inlet, those vacuum thingies generally only suck from a small area at the bottom. For the outlet you need a 1 micron filter

5 acres, Ferguson 35X and implements, Hanmay pto shredder, BMW Z3, Countax ride on mower, chooks, Dorper and Wiltshire sheep. Bosky wood burning central heating stove and radiators. Retro caravan. Growing our own food and preserving it. Small vineyard, crap wine. :)

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7 months 4 weeks ago #558995 by Muz1
When I first came to my patch I had a tank cleaner come and empty the first tank receiving the roof water into his tank truck and then we cleaned the tank using
suction from the truck. Fortunately not much scunge to remove. The outlet to my pump was from the very bottom of the tank so we made a short upstand pipe and the intake is now about 100ml off the bottom. The water was then pumped back into the tank. The second tank was clean so had no treatment. With downpipe leaf traps and a drain cap on the inlet water line our water keeps crystal clear.

Everything Must be Somewhere
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7 months 4 weeks ago #558996 by mattib
Yeah part of our problem is we live in the forest surrounded by some large protected trees, i think mostly Rimu around the house but has those little prickly leaves that get everywhere and dont brush off easily. Previous owner did a half arsed job of protecting the gutter in one tiny spot so one of my summer goals is to put in some decent leaf guards over all the gutters as well as improve the leaf traps.

Its lovely spot to live, but there is one tree hanging over the roof that i would love to remove to improve the water quality as well as let sun into the side of the house and lessen any mould. Missus wasnt up for it until she drew a bath the other night and the water looked like what it actually was, a weak tea made from local herbs and fauna :D

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7 months 4 weeks ago #558997 by Muz1
We have a wattle tree that has fine leaves that are a real pain in the gutters on that side of the house. I have taken out the gutter protectors as the leaves just build up and block the whole gutter. I have a small section of protector over the downpipe so there is mostly only a small section to clear, The downpipe leaf guard traps work well.

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7 months 4 weeks ago #558998 by smudge
As Tony baker said, you need a good rescue plan, honestly you could die within minutes in there
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7 months 3 weeks ago #559024 by mattib
So I have pumped the tank out showing the sediment on the bottom, I see the outlet but there isn’t any second drain outlet. Would you all recommend spraying the insides with some kind of disinfectant, or just brush  down the walls, water blast?

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7 months 2 weeks ago #559027 by tonybaker
Don't use any chemicals for now, after all, you have been drinking that water for a while and it has not killed you yet! Concentrate on getting all that muck out of the bottom maybe using a siphon and long hose to a lower point? or submersible pump . Once you have the inside as clean as possible, deal with coating the inside with whatever you have decided, this is my suggestion as it is solvent free so won't pose a risk to you while you apply it. It seals cracks as well. Once you have done all that, find out why the water is dirty and resolve that issue. Clean the outside of the tank to remove lichen and moss and paint it white, this will prevent the lichen from penetrating the concrete. Sounds daunting but take it slowly and you will get there. Make sure you work with someone whilst you are in that tank!
 

5 acres, Ferguson 35X and implements, Hanmay pto shredder, BMW Z3, Countax ride on mower, chooks, Dorper and Wiltshire sheep. Bosky wood burning central heating stove and radiators. Retro caravan. Growing our own food and preserving it. Small vineyard, crap wine. :)
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7 months 2 weeks ago - 7 months 2 weeks ago #559029 by mattib
Thanks, i figured the same for now and have it all joined up to the gutter again.

Yes i used a submersible pump to drain the remaining part of the tank. The tank has leaned over a little so had about 50 buckets to haul out at the end, wasn't as much silt and muck as i expected so maybe it has been drained and cleaned not so long ago, or maybe my expectations were worse lol. It was mostly grit and sand, i presume it is probably from the concrete tile roof as i used to have the same in our previous house. I did notice that the concrete around the crack and hole was very soft, not sure if that's normal? I didn't end up water blasting as i was worried the whole wall might be a bit soft , probably just paranoid. The grinder easily went in to the mesh so went with a light touch on the soft stuff then used the Betta water plug to fill it again, hopefully that was enough to seal it up, will find out if we manage to get some more rain. If not i will drain again at the end of summer and hit it with that membrane as well as patch a few other bits.

Hole
 

Lone outlet and bottom of tank
 

Living with my head in the clouds in the Waitakere Ranges
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